Recent semiconductor integrated circuits, such as ICs and LSIs, require high productivity, and accordingly, the power consumption of a semiconductor exposure apparatus tends to increase. The feature size of a circuit pattern shrinks more and more, and the environment in the exposure apparatus must be maintained more stably. In particular, as the power consumption increases, an efficient cooling apparatus or heat recovery apparatus, which has a very high temperature stability, is needed.
As a cooling or heat recovery apparatus, one using a refrigerating cycle, which includes a compressor, a condenser, and an evaporator is known (for example, see Japanese Patent Laid-Open No. 2002-48381). According to a cooling apparatus having this arrangement, load heat in an exposure apparatus is recovered by a circulating medium. The recovered heat is shifted to factory cooling water, which is supplied from a factory, has a comparatively high temperature, to perform cooling and heat recovery.
In general, when load fluctuations occur, the rotational speed of the compressor is controlled by an inverter. After heat is recovered by the refrigerating cycle when necessary, the circulating medium is heated again by an electrical heater, or the like, to improve the temperature stability.
In an old-fashioned semiconductor manufacturing factory, the factory cooling water often has a comparatively high temperature of 20° C. to 30° C. In a recent high-productivity factory for semiconductor devices having very small feature sizes, the factory cooling water often has a low temperature of about 10° C. to 18° C.
In the prior art described above, a compressor or reheating electrical heater is used, even when low-temperature factory cooling water is supplied, as in the recent semiconductor manufacturing factory. The power increases to lead to a cooling apparatus poor in efficiency. Also, inverter control and electrical heater control are performed to improve the temperature stability. Accordingly, the number of constituent components increases, the cost increases, and the apparatus becomes bulky.
When the load fluctuates sharply, or the temperature of the factory cooling water fluctuates, sufficient temperature stability cannot be obtained. In some cases, exposure of finer circuit patterns is adversely affected.